1. Field of the Invention
The present invention relates to a boat equipped with an electronic steering device that steers a boat propulsion device such as an outboard motor according to electrical signals coming from an operator's seat side.
2. Description of the Related Art
One of the conventional types of such boats is the one described in JP-B-2959044, in which a boat propulsion device (an outboard motor) having an internal combustion engine and a propeller to move a boat is provided outside of the hull, a steering motor is provided in the connecting area of the hull and the outboard motor for rotating the outboard motor in a horizontal direction, and the steering motor is connected with a steering system representing a boat propulsion device operating unit and provided at the operator's seat, by signal cables (electric wires) capable of sending and receiving the signals. The steering system is provided with a rotational angle sensor. The steering motor rotates to steer the outboard motor based on the rotational direction and the rotational angle of the steering system detected by the rotational angle sensor.
However, in the case of the invention described in JP-B-2959044, there is a possibility of incomplete steering when an output power of the steering motor that performs the steering operation becomes smaller than a steering load due to the low battery charge. Thus, it is desired to provide a control that allows for an effective steering operation.
Besides, in the case of a multiple installation boat in which plural outboard motors are mounted, the steering load is different between the right and the left outboard motors when the boat makes a turn. Also, the steering load changes according to the type of boat on which the outboard motor is mounted, and the running states. In the boat steering device of JP-B-2959044 or in another conventional boat steering device, electric power is generated independently by each boat propulsion device and used to supply power to an auxiliary engine, PTT (power trim and tilt system), an engine starter, and a steering system. However, there is a concern that the electric power to carry out the steering may be insufficient so as to cause response delay under certain conditions such as a heavily loaded boat, a trim-in condition, a high-speed operation, and a sharp turn. Also, there is a concern of cranking failure due to the low battery voltage.